Classic Machines Off-Highway Trucks

Classic Machines: International Harvester’s PayHauler 350 dumptruck

Following on from my article in the May 2009 Contractor “PH65 & 95, the Small Payhaulers”, this month we examine the largest offering from International Harvester, the Payhauler 350. By Richard Campbell.

Developed from the ground-breaking International PH180, the first successful four wheel drive off-highway dumptruck offered by any manufacturer, the PayHauler 350 was also 4-wheel drive and carried a payload of 50 tons.

International Harvester (IH) engineers had considerably refined the PH180 design incorporating quite a few changes along the way, and the end product was styled to match other machines in International’s ‘Pay’ line of earthmoving equipment.

Powered by a Detroit Diesel 16V-71N engine the hauler looked very impressive.

The concept of the machine was that it carried 50 percent of the load on each axle, which made for a very well balanced and stable haul platform.

Four wheel drive allowed for good gradeability, especially as the vehicle had an evenly proportioned load with the added benefit of being able to negotiate soft underfoot conditions without getting stuck.

It could also work in conditions that would shut other jobs down.

IH had quite a niche market for these off highway haulers as no competition existed, and arguably still don’t unless you include ADTs in the equation.

But there aren’t too many 50 ton capacity ADTs on the market designed to carry blasted rock on a daily basis.

IH expanded the range by adding the smaller 35 ton model 330 PayHauler and the 40 ton capacity model 340 to the line as well.

A PayHauler 350B model was introduced in 1978 with the most notable change being in the design and construction of the dump body which had a reduced number of side stiffening members and changes to the air induction system.

By this stage the Cummins VT1710C engine had supplanted the Detroit Diesel 16V-71 as standard power.

When International Harvester imploded in 1982, a separate company was set up by ex-employees called the Payhauler Corporation.

Production was shifted to Batavia, Illinois, where it continued to manufacture and sell the PayHauler 350B and in 1986 introduced a further upgrade to the design, being the PayHauler 350C.

Payhauler Corp offered Detroit Diesel, Caterpillar or Cummins engines as the prime powerplant.

Payhauler Corp was bought by Terex in 1998 and by 2003 Caterpillar had acquired the company.

Since then no new machines have been produced. Caterpillar has elected – so far – not to proceed with any production or further development of the design.

The Payhauler 350 Described

We will examine the PayHauler 350 ’C’ model, introduced in 1986 as it was the most numerous of the three PayHauler 350 models imported into New Zealand

Three optional engines were offered for the 350C but the most commonly installed was the Cummins KT28, a turbocharged V-12 diesel producing 635 horsepower at the flywheel.

This drove a remotely mounted 6-speed Twin-Disc full powershift transmission via a driveshaft. The transmission was approximately mid-mounted in the chassis so the driveline runs from the drop box to the front and rear differentials were not too long.

Top speed of a 350C was approximately 35mph.

Two massive parallel ‘I’ beams formed the backbone of the chassis and almost all of the machines’ vital components were well protected within the chassis rails out of harms way.

Front axle steering was fully hydraulic, accomplished by two identical double acting cylinders.

The PayHauler 350C was shod with dual tyres on both axles, usually 18.00×25, 32-ply and had air operated two-caliper sliding disc brakes on all wheels.

Good old fashioned leaf springs with attendant shock absorbers were the only suspension system offered on the PayHauler and apart from occasional problems with the front leaf spring packs, these performed well in service.

One of the great benefits of the 350 PayHauler was its very low loading height which allowed loading by wheel loader or excavator and presented a good “target” compared to its contemporaries.

The dump body was fabricated from 1000,000 psi high tensile heat treated steel in a ‘mono floor’ design and was raised and lowered by two 3-stage hydraulic cylinders which could hoist the body to its full dump height of 67° in 17 seconds.

Offset to the left was the operator’s cab. This was not particularly large and had a jump seat behind the operator’s seat for a passenger or learner operator.

Full instrumentation was set into a panel that bisected the steering column.

To the right of this panel was the transmission shift control and to the left the body hoist control. All very simple and effective.

Visibility, as with any off highway hauler, was reasonably good to the operator’s left but marginal at best to the right.

Optional Equipment

Three optional bodies were offered for the 350C – heavy duty rock, earth and coal. These could all be exhaust heated if necessary to prevent the load from sticking to the dump bed in cold climates. There was also a wide range of tyres to suit all manner of operating conditions.

The New Zealand Connection

There were around 27 50 ton PayHaulers of all types imported into New Zealand.

Baker Construction was the big user of the IH PayHauler, starting out with two PH180s and then graduating to the 340, 350A, 350B and 350C.

Baker’s fleet saw extensive service all over the Twizel & Pukaki hydroelectric schemes of the 70s and 80s.

Nine of the later model machines are still in service with C&R Developments.

For the Model Collector

Up until quite recently there was not much in the way of IH PayHauler models available.

Ertl offered a couple of rather crude diecasts in odd scales, with undersized wheels, and also a very impressive 1:25th scale kitset model which could be assembled into quite a stunning model – if you were careful.

However, in 2011 First Gear released a diecast 1:25th scale PayHauler 350A that is quite a show stopper and exceptionally well detailed.

Black Rat models also produced a PayHauler 350C to 1:50th scale.

The Black Rat model is beautifully made but virtually unobtainable as it was produced only in very limited numbers (as is the case with all Black Rat models).

The 1:25th scale First Gear PayHauler is not nearly so hard to find, but

is not without its faults and has some minor inaccuracies, mainly in the area of finish. It could well be worth adding to the collection though.

Brief Specifications – Payhauler 350C

Engine:                          Cummins KT28, V12, turbocharged and aftercooled diesel rated at 635 flywheel horsepower @ 2100rpm

Transmission:               Twin-Disc, 6-speed full powershift. All wheels driven

Top Speed:                   35 mph

Brakes:                         Air operated sliding dual caliper on all wheels

Steering:                       Full hydraulic using 2 x double acting cylinders

Turning Circle:               33’ 4”

Std.Tires:                      18.00×25, 32-ply E3

Body Capacity:             50 tons

Hoist:                             Two, 3-stage double acting hydraulic cylinders

Tip Angle:                      67°

Length:                          30’ 3”

Width:                            13’ 3”

Height:                           13’ 4”

Operating Weight:         36.4 tons (empty), 86.5 tons (loaded)

The International 350 PayHauler

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